The invention relates to solid galenic forms of the controlled release tablet type for the instant and then prolonged release of one or more active substances.
The importance of such galenic forms is undeniable. The immediate release of an active substance will ensure its practically instant bioavailability, which is particularly desirable in the case of patients suffering from acute conditions.
However, in the case of active substances having a short half-life, the therapeutic activity is only temporary. Now, a continuous and regular supply of active ingredient is often necessary for an effective therapy. To this end, numerous immediate- and prolonged-release systems have been developed.
Reference may be made, for example, to the following patents and applications of the state of the art: WO 96/03111, U.S. Pat. No. 4,990,335, EP 352 190, BE 905 282, EP 106 443, EP 36 350, EP 615 444 and EP 220 670.
However, in the prior art systems, the kinetics of release of the active ingredient depend on many factors, such as the enzymatic activity and the pH conditions which vary substantially from one individual to another and for the same individual, depending on whether they are on an empty stomach or not.
Furthermore, the pH conditions vary all along the gastrointestinal tract. Thus, it is difficult to predict in vivo, with precision, the profile for the release of a given substance after administration of the prior art instant- and prolonged-release systems.
The present invention aims to solve this problem by providing tablets which preserve their characteristics for the release of active substances regardless of the conditions of administration in vivo.